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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b55f81916618a6023b25e4e76e81cd6b1d2e99ee99615eccb81c3da830c4a68c' 
  AND token = '+6JwzDwkLaX1+6vkXj3GgDYjSYXB2ICikkrw28hnp4k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}